The effect of diet on the compositions of the triglycerides and unesterified fatty acids isolated from the plasma, liver and adipose tissues of rabbits.

Abstract

1. Groups of male rabbits (ten to thirteen per group survived) were givenad lib. a diet consisting of 80 parts of a low-fat basal diet to which were added: for group I, 20 parts maize oil; for group 2, 20 parts butterfat; for group 3, 10parts maize oil and and 10parts butter- fat; for group 4, 0.47 parts maize oil and 43.1 parts wheat starch; and for group 5, 10.2parts maize oil and 21.6 parts wheat starch. The animals in group 6 were givenan ordinary com- mercial rabbit diet. 2. The rabbits were given the various diets for 38 weeks, after which a sample of blood was taken. The rabbits were then killed and the liver and a sample of perine- phric adipose tissue were removed from each animal. The plasma, liver and adipose tissue lipids werefractionated on columns of Florisil and the fatty acid compositions of the tri- glyceride and unesterified fatty acid fractions were determined by gas-liquid chromatography.3. The effects of the different diets on the composition of the unesterifiedfatty acids in the plasma were very similar to the effects of the diets on the fatty acid composition of the plasma triglycerides, but in the plasma unesterified fatty acids the concentration of stearic acid was consistently higher and the concentration of linoleic acid was consistently lower than in the plasma triglycerides. 4. There appeared to be a positive rectilinear relationship between the concentration of stearic acid in the plasma triglycerides and the concentration of triglycerides in the plasma. 5. In the triglycerides of the plasma, the concentrations of palmitic and stearic acids were consistently greater and the concentration of linoleic acid was consistently less than the corresponding concentrations of these fatty acids in the triglycerides of the adipose tissues. In the two groups of rabbits given low-fat diets the fatty acid composition of the liver trigly- cerides was almost identical with that of the plasma triglycerides. 6. In each of the six groups of rabbits the composition of the unesterified fatty acids in the plasma was identical with that of the unesterified fatty acids in the adipose tissues. Inthe unesterified fatty acids of the liver the concentrations of linoleic andarachidonic acids were consistently greater and the concentrations of myristic, palmitic and palmitoleic acids were consistently less than the corresponding concentrations of these acids in the unesterified fatty acids of the plasma and adipose tissues. 7. The results of this investigation are discussedin the light of recent con-cepts on the metabolic relationships between the unesterified fatty acids and triglycerides of the liver, plasma and adipose tissues.